Gary,
my best T10 exit speed to date is 78 mph but that was on my slicks last year. so far I haven't been able to go faster than 75. it's funny because I wasn't recording such high g's on the slicks. not sure if I quite understand how

Makes me question the lap timer, maybe since one has a stiffer sidewall it gives it less pronounced roll. Just a theory who knows. 1.4g's is freakin super high. Anything over 1.1 g's in my car there better be some camber in the turn or I'm going for a spin.

I do think even with stock rotors .8g's under braking still leaves you room to brake harder as long as it's not downhill. I have the same setup stock rotors/calipers w/Ferodo pads and Motul fluid I can hit 1g under braking while going straight or uphill. Downhill depending on the speed is in that .8 -.9 range.

How much negative camber do you run? And how does the sound on your video not sound like wind? Do you have a mic on the back bumper?